Q.The oxidation state of S in S8 is

Ordinary (rhombic/monoclinic) sulphur exists as S8 molecules — octatomic puckered rings.

At ordinary temperatures the most stable allotropes of sulphur (rhombic and monoclinic) are built from S8 molecules, each a crown-shaped (puckered) ring of eight sulphur atoms. Hence the sulphur molecule is …

The clues fit sulphur: S burns to SO2; SO2 turns lime water milky and decolourises acidified KMnO4 (reducing agent); SO2 + O2 -> SO3, which forms H2SO4 (acid rain). Correct option (a).

Decoding the clues:

• X is an amorphous solid that burns in air -> amorphous sulphur. S + O2 -> SO2.
• Y turns lime water milky: SO2 + Ca(OH)2 -> CaSO3 (white/milky) + H2O.
• Y decolourises acidified KMnO4: SO2 acts as a reducing agent, reducing purple MnO4- to colourless Mn2+.
• Y + O2 -> Z: 2SO2 + O2 -> 2SO3; SO3 + H2O -> H2SO4, responsible for acid rain. …

S8 is an elemental (free) form of sulphur; a free element always has oxidation state 0.

S8 is a molecule made entirely of sulphur atoms (a crown-shaped ring of eight S atoms). Since the molecule consists of only one kind of atom bonded to identical atoms, there is no electronegativity difference and no charge separation …